Abstract

Fast electron energy spectra have been measured for a range of intensities between and and for different target materials using electron spectrometers. Several experimental campaigns were conducted on petawatt laser facilities at the Rutherford Appleton Laboratory and Osaka University, where the pulse duration was varied from relevant to upcoming fast ignition integral experiments. The incident angle was also changed from normal incidence to 40° in -polarized. The results confirm a reduction from the ponderomotive potential energy on fast electrons at the higher intensities under the wide range of different irradiation conditions.

Received 07 January 2009Accepted 30 April 2009Published online 18 June 2009

Acknowledgments:

The authors gratefully acknowledge the support of the staff of the Central Laser Facility and of Institute of Laser Engineering in the execution of this work. This work was supported by the UK EPSRC and STFC.

M.N. and R.K. were supported by the CREST, Japan Science and Technology Agency. K.A.T., H.H., and T.T. are grateful to the support from the project: global center of excellence (GCOE) at the Department of Electrical, Electric, and Information, the Graduate School of Engineering, Osaka University, Osaka, Japan and Japan-UK collaboration program of the International Collaboration for High Energy Density Science (ICHEDS) of Japan Society for the Promotion of Science (JSPS) at Osaka University, Osaka, Japan. A part of the research is supported by Grant-in-Aid for Scientific Research of JSPS (Contract No. 19206099) and by Japan/U.S. Fusion Cooperation Program (Contract No. 2036).

J.R.D. and J.V. were supported by the FCT, Grant No. POCI/FIS/59563/2004.

U.S. colleagues were supported by the U.S. Department of Energy under Contract Nos. W-7405-Eng-48, DE-FC52-08NA28302, DE-FC52-92SF19460 (Office of Inertial Confinement Fusion), and DE-FC02-ER54789 (Fusion Science Center, Office of Inertial Fusion Energy Science), the University of Rochester, and the New York State Energy Research and Development Authority. The support of DOE does not constitute an endorsement by DOE of the views expressed in this article.